Experimental Research On Deformation Characteristics Of Sand Foundation Under The Action Of Rigid Foundation

With the vigorous development of infrastructure construction in China,all kinds of buildings are erected.However,the construction and operation of all the buildings are inseparable from the stable foundation.Therefore,the deformation characteristics of the foundation soil are an important research content.Based on the research of "China Railway Corporation Science and Technology Research and Development Program","Super Deep and Large Section Caisson Foundation Design Theory and Key Technology Research",this paper do the research through the indoor model static load test and supplemented by numerical simulation.we designed the test groove and three different sizes of concrete model with corresponding rigid floor,carried out five static load test under the condition of different foundation width and different burial depth,through the displacement meter and soil pressure sensor to monitor the entire process of loading test,we got the data of foundation settlement and additional stress in soil for analyzing the damage process of the foundation,the distribution and variation law of the base stress during the loading process,the distribution and the variation law of the stress in soil,the law of unloading rebound deformation after the foundation fail and bearing characteristics of the soil under repeated loading under different foundation width and different burial depth.Following conclusions are obtained:(1)Through static load test and numerical simulation,it is found that the damage of sand foundation has obvious progressive failure characteristics.The foundation bottom stress has a significant redistribution with the gradual destruction of the foundation soil.At the beginning of the loading,distribution of the foundation bottom stress are uniformly increased.With the loading process,when the load increases to the limit of the ratio,the foundation bottom edge stress of the five groups is no longer increased by the increase of the load,The results show that the damage of the foundation is gradually increased from the foundation edge to the foundation center,indicating that the damage range is gradually increased.At this time,the bearing capacity is mainly provided by the soil near the foundation center.(2)At the beginning of the loading,the vertical additional stress in the soil is basically increasing uniformly.When the test is loaded into the ratio limit,the bearing area of the soil is reduced due to the destruction of the soil under the edge of the foundation bottom.The vertical additional stress of the foundation center is much higher than that of the foundation edge,the variation is not as much as that of the soil near the foundation bottom where the soil is far from the foundation.(3)At the beginning of the loading,the horizontal additional stress in the soil is gradually increasing uniformly.The peak of the horizontal stress in the soil appears in the upper part at first,and gradually move downward with the increase of the load.When the load reaching the ultimate load,the horizontal additional stress peak of soil under the foundation edge appears at the position of one time the foundation width below the foundation bottom.The horizontal additional stress peak in the soil below 0.5 time the foundation edge appears at 1.5 times the foundation width below the foundation bottom.(4)According to the analysis of vertical additional stress in soil,the vertical additional stress diffusion angle θ is 18.4°<0<26.6°,it is consistent with Code for design of building foundation.(5)The unloading rebound curves obtained from five groups were very smooth,with an overall rebound about 10 mm and most of the rebound deformation occurred at the final stage of unloading.The width and the burial depth of foundation have effect on the rebound deformation.Compared with the different width,it is found that when the unloading ratio is the same,the bigger the foundation width is,the smaller the rebound is.Compared with the different burial depth,it is found that when the unloading ratio is the same,the rebound of no buried depth group is less than that of the other two groups,but the other two groups are basically the same.(6)When the loading is repeated,it is found that the foundation has the bearing capacity after the overall destruction,and the bearing capacity is greatly improved compared with the initial loading.The compressive modulus of the soil is 1.84-2.25 times higher than that of the initial loading,and the width and burial depth of foundation have effect on compressive modulus.Compared with the different width it is found that the compression modulus ratio increases with the increase of the foundation width,and the growth is basically linear.The comparison of the different burial depths shows that the compression modulus ratio increase with the increase of burial depth and the non-linear growth appears.The larger the foundation burial depth is,the faster the compression modulus ratio increases.